The applied method is a result of development and enhancement of the method of impact crushing of the U.S. Pat. No. 5,328,103 which we call a method of active impact crushing. FIG. 1 shows the motion of mineral pieces a) while coming along a feed track and into a zone of rotor rotation and b) during the scattering of the pieces after an initial impact.
The U.S. Pat. No. 5,328,103 discloses the method, when the mineral pieces of different sizes come along the feed track into the zone of the rotor rotation. It was assumed that the size of a piece coming into contact with the rotor does not matter and velocity vectors of the pieces thrown off towards rotatable secondary crushing rotors depend only on the amount of their travel along the impact surface of the rotor.
The described method is implemented by impact crushers of different power and output, which are disclosed in the U.S. Pat. No. 5,328,103 as well, and is used in real industrial operating conditions in the processing of ore and non-metallic mineral. In such an impact crusher secondary crushing rotors (rotors of the secondary crushing) are rotatable synchronously with the rotor (the initial crushing rotor) and have concavo-concave impact active reflecting surfaces, wherein their masses increase from the centers of the rotor rotation along the general symmetry axes, and the radiuses of the active reflecting surfaces are equal to the distance from the point of crossing of the feeding track plane and the circumference of the initial crushing rotor to the common active reflecting surface of the secondary crushing rotors. In this crusher the initial crushing rotor operates as a forwarding rotor, which forms the portions of the material to be crushed, partially crushing the pieces of the material to be crushed and forwards them towards the secondary crushing rotors (reflecting elements), which crush the arriving material to particles of a certain size depending on the set modes by use of the method using the active impact and therefore they are called the rotors of active impact. Additionally, a principle of counter and high-speed dynamic interaction of impact elements and material to be crushed is carried out.
The crushers using the active impact have high efficiency of crushing and grinding of mineral and can avoid multistage and multiprocess ore pretreatment. Despite the advantages, the method has shortcomings. During the use of the crushers it was seen that the crushing efficiency is limited, processing time is increased and regrinding of the crushed product occurs, which leads to unnecessary energy consumption.
It is known in the ore mining that the ore regrinding leads to significant losses of useful components during the enrichment process. The production of the regrinded material with the size of particles less than 2 to 4 millimeters is extremely undesirable in the construction material industry, especially in highway engineering, because such material is not used and this leads to adverse economic and ecological side effects. This is typical, for example, for jet mills, devices using the method of “the step crushing”.